This proposal seeks to add a cost component to an ongoing study of two approaches to treatment of people who are, dually diagnosed with severe mental illness and substance use disorders. The study compares traditional Community Support Program (CSP) case management with a program that integrates treatment for substance abuse and psychiatric disorders in an assertive case management approach we call Continuous Treatment Teams (CTT). Approximately 230 clients will be randomly assigned to either CSP or CTT and followed over a three-year period to evaluate the relative effectiveness of the two approaches. Because of difficulties associated with co-occurring severe mental illness and substance use disorders, these clients are believed to be particularly high resource users. One goal of the proposed study is to collect accurate client-level data on resource use. By combining data on resource use at several points in time with the extensive data on effectiveness that are already being collected as a part of the original study, we will be able to compare the cost-effectiveness of the two approaches over time. We hypothesize that total resource use by CTT clients will decrease over time, even though the initial investment per patient may be greater than that of the CSP approach, and that CTT will be more cost-effective than CSP within the three-year follow-up period. Measuring resource use and effectiveness at regular intervals allows us to test these hypotheses by tracking changes in cost-effectiveness over time. Questions of community and family burden have become more important as severely mental ill patients spend less time in hospitals and more time at home or in the community. Previous mental health cost studies used indirect methods for estimating community and family costs, measured them incompletely, or failed to measure them at all. In this study we will improve on existing techniques for documenting use of community and family resources. We will use newly developed client and family interviews to capture these costs more accurately. We hypothesize that CTT clients will use fewer family and community resources than CSP clients during the follow-up period.